The coalition is unlikely to meet its target of providing 150,000 new affordable homes in Britain over the next four years because its figures "simply do not stack up", new analysis claims.

According to the accountancy practice Beever and Struthers, the lack of funding will leave ministers with a shortfall of 19,000 properties.

The statement by the chancellor, George Osborne, that £4.4bn will be available to fund the commitment, has ignored the fact that after existing commitments are met, only £1.9bn will be left for new capital spending to meet the target, say the accountants. The £1.9bn would only fund 32,000 new homes, Beever and Struthers says.

The policy of allowing housing associations to charge higher rents could finance another 39,000 homes, and 60,000 homes could, at a generous estimate, be created from grants already allocated, says the accountants' report, Reforming the Social Housing System. But that would still add a maximum of 131,000 homes – short of the 150,000 promised.

The Department for Communities and Local Government was one of the biggest losers in the government's spending review, released in October, in terms of proportion of money cut. Its capital expenditure budget is to be slashed by 60% by 2015.

Nick Stevens, a partner at Beever and Struthers, which specialises in providing audit services to the social housing sector, said: "Much more heat than light has been generated over the past few months as UK social housing gets set to undergo the most radical changes in decades. But important though debates about housing benefit reform and intermediate rent tenancies are, they mask the real issue that prevents millions of people finding decent accommodation: chronic long-term shortage of supply."

Social housing providers need to think about exploiting different sources to plug the gap, such as investment in new properties by pension funds, Stevens said. In return, the funds would get stable, long-term income. "They are the only viable method of reversing the desperate lack of social housing which impacts so severely on so many of the most vulnerable in our society," he said.

A spokesman for the Department for Communities and Local Government said: "The major reform of the social housing sector that we announced last month will ensure that social housing helps as many people as possible whilst protecting the most vulnerable in society.

"It will enable housing associations to make better use of stock and introduce more flexibility on rents and tenancies, and ensure that those in greatest housing need are given priority.

"By offering people the helping hand they need, when they need it, associations will become even more effective at helping people get back on their feet. But above all it will be fairer – [associations] will now be able to make decisions that genuinely meet the needs of local people, and the changes will not any affect any existing tenants."